New Lower Thames Crossing

[jackal]

... Despite the longer tunnels, using TBMs, it would turn out to be lower in both cost and all adverse impacts. ...

The bored tunnel for this option appears to be some 7.5 miles, three times longer than the proposal. ...
... This is 23% more than the £5.3bn contract cost for the LTC as developed.

My estimate that the option A14 total cost would be lower than the current plan was my own amateur estimate, based on the simplicity of the task: one twin tunnel, two TBMs, two over-bridges for the forks, and a bit of M25 widening here and there. TBMs are expensive, but not all that expensive. Immersed tube segments are also expensive, and tricky to handle. The technology and usage of TBMs seems to be quickly advancing. However, I accede to your more rigorous estimating.

I was also influenced by hearing a rumour, mid-this-year, that the Sydney Western Harbour Tunnel, planned so far to be immersed tube, was considering a switch to TBM. Today, that rumour was confirmed -
https://www.smh.com.au/national/nsw/maj ... 5bv0g.html

Still not very rigorous!

Just to clarify, the LTC tunnels will also be bored. Immersed tube and bridge alternatives were considered but rejected. The price for the immersed tubes was pretty much the same as the bores while having more environmental impact. Either way you are looking at 5-10 times the cost of a surface route.

[RichardA35]

I have mentioned it before and I may have missed the answer, but when the tunnel was increased in bore from D2 to D3, I don't believe the early discarded options (along A route corridor particularly) were tested again for cost and benefit as the economics could have been changed significantly by this decision. I think the only option tested for D3 was the chosen one via Tilbury.
The benefits to the Dartford Crossings of another D3 adjacent would presumably be fairly major although the costs would also be greater.
Could someone point me to this appraisal if it were done.

[JackieRoads]

The new 'local refinement' consultation is open. While the road design is largely as before there are a few differences:

1. As anticipated, there's a new slip connecting Orsett Cock to the A1089. This has quite wide ranging implications, as not only local traffic but northbound and southbound LTC traffic can now access the A1089 via a U-turn at Orsett Cock. This new connectivity comes at a cost, as the direct link from the westbound A13 to the A1089 has had to make way (the movement can still be performed via Orsett Cock). Here's the before and after:


A13 2021 - Copy.JPG


A13 2022 - Copy.JPG


So basically one freeflow movement is sacrificed for the sake of several at-grade movements. On balance I think it's a decent trade, as A13 westbound to A1089 does not seem to be a huge movement (<250 PCU in a peak hour), and there were some notable missing movements in the previous design that, as shown above, would have forced strategic traffic heading for the A1089 onto local roads.

2. The Tilbury GSJ has returned, this time for operational access, though "with possible future development in mind, helping to avoid potentially disruptive re-work at a later date. ... Any new road connecting to the LTC at this point would have to follow the relevant planning process at the appropriate time". I think it's okay really. It does make sense for NH and emergency services to be able to turn around near the tunnel, and it would save some further work on the LTC in the event of the Tilbury link road. Even so, I think some work would be required, as it's quite a skimpy folded diamond with a single carriageway bridge and link roads.


Tilbury 2022 - Copy.JPG


3. It doesn't seem to be mentioned in the guide, but I noticed that the M25 between the LTC and A127 now has full hard shoulders. They were discontinuous in the previous design, to the point of being ALR-like southbound, which is of course verboten.

Consultation: https://highwaysengland.citizenspace.co ... tion-2022/
Guide: https://highwaysengland.citizenspace.co ... tation.pdf
Interactive map: https://ltcconsultation2022.nationalhighways.co.uk/map/
General arrangements: https://highwaysengland.citizenspace.co ... ements.pdf

Any idea if Tilbury Services or smth will be included?

[jackal]

^ I've not heard of any Tilbury Services, and access to Tilbury from the new road will be poor (there is a separate scheme that might address this).

I have mentioned it before and I may have missed the answer, but when the tunnel was increased in bore from D2 to D3, I don't believe the early discarded options (along A route corridor particularly) were tested again for cost and benefit as the economics could have been changed significantly by this decision. I think the only option tested for D3 was the chosen one via Tilbury.
The benefits to the Dartford Crossings of another D3 adjacent would presumably be fairly major although the costs would also be greater.
Could someone point me to this appraisal if it were done.

I don't think it was done. But it's hard to see that a new D3 would improve the case for a more online ("location A") solution.

The location A solution that got furthest, "Route 1", was a really neat design as it meant the existing northbound tunnels would become the fast lanes in both directions (lanes 4 and 5 at the merges/diverges). So effectively you would get more than just two extra lanes - the existing lanes would also be allocated more efficiently, discouraging HGVs from using the tunnels. This was possible because it was proposed to add a four lane northbound bridge to the west, allowing a mirrored arrangement with the existing southbound bridge.

I'm not sure if you're suggesting a six lane bridge or two three lanes bridges or tunnels, but in any case it doesn't allow for the same efficient use of the existing tunnels as there is no mirroring of the existing bridge. Also two three lane bridges or tunnels would be very expensive compared to one four lane bridge, while a six lane bridge would probably have to split lanes across two carriageways, making it nearly twice as wide as the four lane bridge.

So you're basically going from adding "2 and a half lanes" (two new lanes plus better utilisation of existing infrastructure) under Route 1 to adding three, which is unlikely to justify the huge further cost.

Additionally the proposal you mention would seem to require D6 through here, which may not be practicable.

You can see the route 1 design here: https://highwaysengland.citizenspace.co ... of%205.pdf

[Peter Freeman]

Just to clarify, the LTC tunnels will also be bored. Immersed tube and bridge alternatives were considered but rejected.

Oops! I just reviewed early pages in this thread and see that I was very out-of-date, with TBM being confirmed by 2019 or earlier. There's some very interesting reading to be had in those old posts, and many fascinating digressions!

[Peter Freeman]

I know it's much too late now, but the more I look at it, the more I think the LTC/A13/A1089 interchange is an awful mess. The root of the problem is Tilbury access. If A1089 is left out of the picture, the LTC/A13 interchange becomes so easy, especially as, with the skew, only half the normal movements need to be provided.

Of course, major port Tilbury should be connected. Otherwise, you'd probably have to place warning signs on M25 southbound, preceding the fork, that instruct "For Tilbury, continue on M25 to A13". (Or, at least, sign it really well on the gantries). Omitting Tilbury altogether is an option worth considering though.

A thought: instead of complicating LTC/A13 with the A1089 connection, build a Tilbury link a little way southwards, closer to the tunnel? Not where previously planned (near to Tilbury East) - that would add distance. Connect it near to West Tilbury, so it heads SW.

Another thought, to simplify the planned LTC/A13/A1089 braiding tangle, is to use some major signalisation for the A1089 or other Tilbury link. A multi-lane SPUI or DDI - somewhere!? Sorry, I have no design - just a thought. Too late now anyway.

[jackal]

Of course, major port Tilbury should be connected. Otherwise, you'd probably have to place warning signs on M25 southbound, preceding the fork, that instruct "For Tilbury, continue on M25 to A13". (Or, at least, sign it really well on the gantries). Omitting Tilbury altogether is an option worth considering though.

A thought: instead of complicating LTC/A13 with the A1089 connection, build a Tilbury link a little way southwards, closer to the tunnel? Not where previously planned (near to Tilbury East) - that would add distance. Connect it near to West Tilbury, so it heads SW.

Even with the proposed design the A1089 can only be reached from M25sb via J30 and the A13. Connections are asymmetrical as it's a lot easier to get through J30 in that direction, which is freeflow.

The A13 interchange design is a suboptimal compromise that's been reached because the Tilbury link was canned at a relatively late stage due to local opposition; I imagine the same would apply to your version of the link. The link was also only proposed at quite a late stage, and if it had been proposed earlier there might have been time to iron out the kinks and include it, simplifying the A13 junction.

As mentioned before, the A13 junction would also have been much simpler under route 2 (which merged with the A1089 at the current GSJ near Tilbury for a four lane section up to the A13) or route 4 (which had a stack with the A13 further to the east). I doubt they'd have selected route 3 if they'd thought through all the movements required at the A13 junction, and hence its expense.

[BF2142]

Am I understanding this correctly - the LTC, designed to relieve the Dartford Crossing bottleneck, won't have a junction with Tilbury. So all HGV traffic will continue to use the DC.

[Peter Freeman]

I'll preface this post with, again, 'it's too late now'. But Sabre comments before design finalisation presumably have no more effect than our comments after it, so we may as well indulge ourselves.

I doubt they'd have selected route 3 if they'd thought through all the movements required at the A13 junction, and hence its expense.

Could I paraphrase that statement as "If they'd designed more thoroughly before going public with consultation, and if they'd re-appraised all options after consultation caused deletion of the Tilbury link near the tunnel portal, then they wouldn't have painted themselves into this corner" ? (The implication being that the design has progressed so far that they're too embarrassed to withdraw it now),

Even with the proposed design the A1089 can only be reached from M25sb via J30 and the A13.

I hadn't noticed that (oops again ). I now propose that Tilbury-to-M25 should use the existing A1089+A13 route in both directions, J30 gets a 90-degree flyover for M25 N to A13 E, and LTC zooms on the proposed alignment directly to the tunnel with no intermediate interchanges. I still think this corner-cut route is marginally better than option A14 (long express-lanes in bored tunnel), even without servicing local needs.

In retrospect there are probably three other options I'd prefer over the current plan. BUT, it's too late now !

[jackal]

As mentioned above, the DCO application was made on 31 Oct. The application documents are now available. The Funding Statement indicates a capital cost of £5.2 billion to £9.0 billion, including CPOs.

PINS have 10 more days to accept or decline the application for examination. This is an impactful decision - their previous dissatisfaction with it resulted in a two year delay before this reapplication.

The only highway design change I've found compared to the consultation 6 months ago is that the east bound offslip joining Orsett Cock is three lanes rather than two. The roundabout itself is unchanged from the improvements made in the A13 widening scheme.

General arrangement sheets 1-20: https://infrastructure.planninginspecto ... %2020).pdf
Sheets 21-49: https://infrastructure.planninginspecto ... %2049).pdf
PINS scheme page: https://infrastructure.planninginspecto ... -crossing/

Am I understanding this correctly - the LTC, designed to relieve the Dartford Crossing bottleneck, won't have a junction with Tilbury. So all HGV traffic will continue to use the DC.

The A1089 and Tilbury are accessible from the LTC via the A13 junction complex.

[AnOrdinarySABREUser]

I think your analysis may be correct if the focus is only on alleviating congestion on, and around, the bridge. That option simply adds express lanes that bypass the bridge and three busy junctions. Despite the longer tunnels, using TBMs, it would turn out to be lower in both cost and all adverse impacts.

However, the NH proposal partially unloads the Dartford crossing and then does more. It's a short-cut for N-SE traffic, and provides bonus local connections. Now-deleted local connections (eg. Tilbury) north of the river would have further exploited this tunnel, at relatively low cost.

That's a good point, to be fair. I thought that the connection between the A2 westbound and A282 northbound and vice versa were enough to fulfill the demand alongside the existing junctions, but NH does make a fair point in that regard. I only really thought about relieving congestion at the crossing (one of NH's main points they used to justify the new LTC) as well at mitigating the environmental impact of the scheme, but I think that the new local connections and stuff are just unnecessary; cutting down the time between Kent and Essex is unnecessary and the A13 serves the area well enough (from my experience, maybe not the case at rush hour!).

PS. Sorry for the late response, didn't see it!

[jackal]

A new flythrough has been posted:



As we knew the LTC will be the A122, the main remaining number issue was whether the road between the A289 and LTC junction would be A2 or M2. The video says "A2/M2" near the westbound diverge for the A289. But the engineering drawings are clearly marked "A2" for the mainline, and then "A2/M2 Mainline" near the eastbound A289 merge (see here, especially penultimate drawing).

So the logical conclusion is that there will be a "random" change from M2 to A2 and vice versa near the A289 diverge and merge. Of course, it is usual to have a motorway-A road transition at a merge or diverge, but these ones will both be the "wrong way round" - e.g., eastbound you will go A2 to M2 at the merge rather than (as at present) the diverge, so the escape route for non-motorway traffic is lost. This is because the eastbound diverge and westbound merge are being removed but NH seemingly want to keep the transitions in similar locations.

This is not very surprising given similar bodges at Catthorpe and elsewhere, but it's absolutely stupid given the hazard created for non-motorway traffic, and the unnecessary recurring cost of escorts to get them off the motorway. All they needed to do to avoid this was extend the M2 along the D4H A2 as far as the LTC junction, and of course no non-motorway traffic should be on this road anyway, as it unavoidably leads to/from the M2. No engineering change would be required other than blue signs.

[Truvelo]

Is there any change to the road or junction layouts in that new video?

[jackal]

Is there any change to the road or junction layouts in that new video?

I think it's just a visualization of the DCO application design that was published in November, which was itself almost identical to the previous version (see my post of 17 Nov).

Also I should mention the scheme was accepted for examination on 28 Nov, which is a milestone given it was knocked back last time leading to a long delay.

[Peter Freeman]

A new flythrough has been posted: ...

It's good to see a flyover version that matches the latest design. However, the video's from a high level and doesn't have great resolution, so it's difficult to see lane details (not a big deal - we see them clearly elsewhere). Also, it doesn't show quite the full extent of the A13 interchange, so the Orsett Cock roundabout calamity isn't visible.

Having now had more time to ruminate on that, I've become more and more dissatisfied with the mess. Really! - sending Tilbury traffic eastward along (or parallel to) an unrelated road (A13), in order to do a U-turn at a roundabout, in order to reach another road (A1089) south-westward, is desperate and un-professional, isn't it?

[jackal]

It is hopefully just temporary as there's a separate £200m Tilbury access scheme.

[Peter Freeman]

It is hopefully just temporary as there's a separate £200m Tilbury access scheme.

Do we have details of, or a discussion topic about, this?

[jackal]

It is hopefully just temporary as there's a separate £200m Tilbury access scheme.

Do we have details of, or a discussion topic about, this?

It's just a line in the DfT contract spreadsheet:

Tilbury Port Access
Procurement start: 01/09/2024
Contract commencement: 03/03/2025
£200,000,000.00

[Peter Freeman]

I'm skeptical that it will replace the Orsett Cock u-turn. There's too much concrete being poured there for it to be temporary. Sad.

[jackal]

I'm skeptical that it will replace the Orsett Cock u-turn. There's too much concrete being poured there for it to be temporary. Sad.

No concrete will be poured for the Orsett Cock u-turn so far as I know as the slips are needed for other movements. Only the freeflow A1079 to LTC south slip would be redundant if they built a more direct connection, which isn't the end of the world.